[wasm] Add JSToWasmWrapperCache to reuse generated wrapper code

src/signature.h

Index: src/signature.h
diff --git a/src/signature.h b/src/signature.h
index 32050fe4b0178476d296672ba8fe8dee6dd41a52..519138bec39cfaee68c54d31cd23497ff3b65bf3 100644
--- a/src/signature.h
+++ b/src/signature.h
@@ -32,7 +32,7 @@ class Signature : public ZoneObject {
     return reps_[index];
   }
 
-  bool Equals(Signature* that) {
+  bool Equals(const Signature* that) const {
     if (this == that) return true;
     if (this->parameter_count() != that->parameter_count()) return false;
     if (this->return_count() != that->return_count()) return false;